Prepare for the removal of HH\Lib\Path

Fix compatibility with 4.93 and HSL IO v0.3

compatibility updates (#32)

* Permit HSL IO v0.2

* Add FIXME whitelists

* actually only require HSL IO v0.2

* API changes for HSL IO v0.2

Permit type-assert v4 (#31)

Co-authored-by: Daniel Jakob <github@usox.org>

Support (and require) hsl-experimental 4.52

Upstream changes:
- blocking functions renamed
- readAsync/writeAsync no longer deal with the whole thing

Other changes made here:

- do a chunked copy instead of using readAll/writeAll to reduce peak
  memory
- that means we're making multiple calls with different return values,
  which I don't see how to mock. Use a pipe handle instead of a
  mock in the unit test.

support (and require) hsl-experimental v4.50

fix renamed IO interface

fix renamed IO interface

Apply stricter typchecker options.

Depends on updated hackmock.

support HSL 4.25+